Adding format.json during FS initialization (#1896)

fs-v1-metadata.go

@@ -7,7 +7,8 @@ import (
 )
 
 const (
-	fsMetaJSONFile = "fs.json"
+	fsMetaJSONFile   = "fs.json"
+	fsFormatJSONFile = "format.json"
 )
 
 // A fsMetaV1 represents a metadata header mapping keys to sets of values.
@@ -78,6 +79,34 @@ func newFSMetaV1() (fsMeta fsMetaV1) {
 	return fsMeta
 }
 
+// newFSFormatV1 - initializes new formatConfigV1 with FS format info.
+func newFSFormatV1() (format formatConfigV1) {
+	return formatConfigV1{
+		Version: "1",
+		Format:  "fs",
+		FS: &fsFormat{
+			Version: "1",
+		},
+	}
+}
+
+// writes FS format (format.json) into minioMetaBucket.
+func writeFSFormatData(storage StorageAPI, fsFormat formatConfigV1) error {
+	metadataBytes, err := json.Marshal(fsFormat)
+	if err != nil {
+		return err
+	}
+	// fsFormatJSONFile - format.json file stored in minioMetaBucket(.minio) directory.
+	n, err := storage.AppendFile(minioMetaBucket, fsFormatJSONFile, metadataBytes)
+	if err != nil {
+		return err
+	}
+	if n != int64(len(metadataBytes)) {
+		return errUnexpected
+	}
+	return nil
+}
+
 // writeFSMetadata - writes `fs.json` metadata.
 func (fs fsObjects) writeFSMetadata(bucket, prefix string, fsMeta fsMetaV1) error {
 	metadataBytes, err := json.Marshal(fsMeta)

fs-v1.go

@@ -39,6 +39,16 @@ type fsObjects struct {
 	listObjectMapMutex *sync.Mutex
 }
 
+// creates format.json, the FS format info in minioMetaBucket.
+func initFormatFS(storageDisk StorageAPI) error {
+	return writeFSFormatData(storageDisk, newFSFormatV1())
+}
+
+// loads format.json from minioMetaBucket if it exists.
+func loadFormatFS(storageDisk StorageAPI) ([]byte, error) {
+	return readAll(storageDisk, minioMetaBucket, fsFormatJSONFile)
+}
+
 // newFSObjects - initialize new fs object layer.
 func newFSObjects(disk string) (ObjectLayer, error) {
 	storage, err := newStorageAPI(disk)
@@ -48,7 +58,20 @@ func newFSObjects(disk string) (ObjectLayer, error) {
 
 	// Runs house keeping code, like creating minioMetaBucket, cleaning up tmp files etc.
 	fsHouseKeeping(storage)
-
+	// loading format.json from minioMetaBucket.
+	// Note: The format.json content is ignored, reserved for future use.
+	_, err = loadFormatFS(storage)
+	if err != nil {
+		if err == errFileNotFound {
+			// format.json doesn't exist, create it inside minioMetaBucket.
+			err = initFormatFS(storage)
+			if err != nil {
+				return nil, err
+			}
+		} else {
+			return nil, err
+		}
+	}
 	// Return successfully initialized object layer.
 	return fsObjects{
 		storage:            storage,

object-common.go

@@ -126,6 +126,7 @@ func cleanupDir(storage StorageAPI, volume, dirPath string) error {
 		}
 		for _, entry := range entries {
 			err = delFunc(pathJoin(entryPath, entry))
+
 			if err != nil {
 				return err
 			}